1. Field of the Invention
The present invention is directed to a radiation detector for use in an X-ray computed tomography apparatus.
2. Description of the Prior Art
A photodiode array for an X-ray detector of a computed tomography apparatus is disclosed in German OS 44 42 853 wherein a number of photodiodes are arranged in row form on a substrate. A connection of an optically active region of each photodiode leads away from its narrow side and forms a contact on the substrate. The contact is connected to an electronic evaluation unit via a wire. A further connection of the photocathode is formed e.g. by the substrate.
This known photodiode array is not suitable for constructing densely packed multi-row photodiode arrays, because it is necessary for a multiplicity of wires to be routed away between each row. Moreover, the contact connection and laying of the wires is costly and time-consuming.
German OS 35 03 685 also discloses a detector for computed tomography apparatus having a number of photodiodes arranged in row form, the photodiodes each being formed from a substrate and an optically active region provided at the top side of the substrate, and a scintillator being applied on the optically active region. The optically active region is in each case provided with an electrical connection which extends as far as the underside of the substrate of the photodiode.
German OS 198 41 423 discloses a detector for a computed tomography apparatus which is composed of a multiplicity of individual detectors and whose individual detectors are mounted on a printed circuit board, which produces the required electrical connections also to the individual detectors with contacts opposite the latter.
An object of the invention is to provide a detector for an X-ray computed tomography apparatus which is constructed as compactly as possible and which can be fabricated as simply and cost-effectively as possible.
This object is achieved in accordance with the invention by a detector for a computed tomography apparatus having a number of photodiodes arranged in row form on a printed circuit board, wherein the photodiodes are in each case formed from a substrate and an optically active region provided at the top side of the substrate and a scintillator is applied on the optically active region, and wherein an electrical connection of the optically active region, which connection extends to the underside of the substrate, is opposite a first contact arranged on the top side of the printed circuit board. The electrical connection has a second contact provided at the edge of the optically active region and a metallization layer is provided on the underside of the scintillator, the underside facing the optically active region, so that when the scintillator is mounted, the second contact is connected to an electrical conductor which is provided at the outer periphery of the substrate and is arranged in a gap formed between two adjacent photodiodes. The inventive detector thus is constructed particularly compactly. It can be fabricated cost- effectively. The opposite arrangement of the first contact and the connection enables direct contact connection. Wiring is not necessary.